Channels of type Streamed Media may support the Media Signalling interface.
If not, the connection manager is assumed to be presenting the media
streams to the user automatically (for instance, in a connection manager
like gnome-phone-manager or telepathy-snom that remotely controls a
telephone, the phone's own speaker and microphone will probably be
used directly).

If Media Signalling is supported, the Telepathy client is responsible for
actually streaming the media, using the Media Signalling interface to
provide signalling (connection managers might implement this interface in
terms of Jingle or SDP, for instance).

Channels of type Streamed Media may also support the DTMF and
CallState interfaces.